[issue37652] Multiprocessing shared_memory ValueError on race with ShareableList

[mental]

mental <m3nta1 at yahoo.com> added the comment:

Interestingly enough the race only seems to occur when the mutator resets the index with an identical value (try replacing the setitem value with: `not X[0]` or populate from `[b'hi']` and with the mutator code use `X[0][::1]`.

I can't help but think to implement an internal cache that would store the hash of the last modified value, then when another set occurs compare the two hashes and have the operation be a no-op if they match (thoughts?).

In the meantime I'll continue investigating to see what exactly causes this quirk :)

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue37652>
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